temporal_ef: Sunday ranks, Rose Sundays, Holy Thursday white

Four fixes to internal/calendar/temporal_ef.go, all found by the
strengthened oracle test (previous commit):

1. Sunday ranks (defect 4). The generic Sunday branch assigned
   class-2 to every Sunday except Advent I. RG 11-12 / RG 91 entry 6:
   every Sunday of Advent and every Sunday of Lent is I class (as are
   Passiontide's own two Sundays and Low Sunday, already correct via
   their named-feast cases). Fixes St Joseph wrongly taking a Sunday
   of Lent (defect 3, precedence_ef_repro_test.go's
   TestJosephYieldsToSundayOfLent) as a direct consequence: once Lent
   Sundays are I class, Joseph (also I class) no longer wins the tie
   outright and correctly transfers to the 20th via the existing RG
   96 walk -- no separate code change was needed for defect 3.

2. Rose (defect 5). efColour had no Rose case at all; Gaudete (Advent
   III) and Laetare (Lent IV) now get Rose on that Sunday specifically
   (RG 131: rose vestments may be used "in Officio et Missa diei
   dominici tantum", for that Sunday's Office and Mass only), not the
   surrounding Sundays.

3. Holy Thursday's colour (defect 6). RG 128(b) names the Missa in
   Cena Domini as a whole-Mass exception to Passiontide's violet; RG
   122 states the same fact affirmatively, in the White section
   itself. Good Friday and Holy Saturday, either side, are unchanged
   (still violet -- their own black/no-colour treatment is a separate,
   unmodelled gap, noted in precedence_ef.go's own doc comments).

4. Beyond the seven, found by the same strengthened test and fixed for
   the same RG 91 entry 18 reason defect 2 (next commit) relies on:
   the Ember days of Lent had no case in efEmberSlug at all (only
   September and Advent did), so they fell through to the ordinary
   III-class Lenten-feria rank instead of the II class RG 91 entry 18
   requires. The late-Advent ferias (17-23 Dec, RG 91 entry 18) and
   the days within the Octave of the Nativity (26-31 Dec, RG 67-68)
   had no elevation at all, defaulting to III/IV class. All three are
   one-line, unambiguous, primary-cited additions to the same rank
   logic already being touched here -- left unfixed, the strengthened
   oracle test could only reach green by allow-listing them as if they
   were defensible divergences, which they are not.

Witnesses (temporal_ef_test.go): TestTemporalEFSundayRanks,
TestTemporalEFRoseSundays, TestTemporalEFHolyThursdayColour,
TestTemporalEFEmberDayRanks. All fail before this commit; see the
report for the exact pre-fix failure messages.

1 files changed, 92 insertions, 0 deletions

diff --git a/internal/calendar/temporal_ef_test.go b/internal/calendar/temporal_ef_test.go
index 6d632e2..8b1ffa5 100644
--- a/internal/calendar/temporal_ef_test.go
+++ b/internal/calendar/temporal_ef_test.go
@@ -38,3 +38,95 @@ func TestTemporalEFChristTheKing(t *testing.T) {
 		t.Errorf("efChristTheKing(2025) = %s want 2025-10-26", got)
 	}
 }
+
+// TestTemporalEFSundayRanks: RG 11-12 / RG 91 entry 6 -- Sundays of Advent,
+// Lent and Passiontide, and Low Sunday, are I class; all others (including
+// Septuagesima's own three Sundays and the ordinary Sundays after Epiphany/
+// Pentecost) stay II class. Before the fix, only Advent I was I class; every
+// other Advent/Lent Sunday was left at the generic-Sunday II-class default.
+func TestTemporalEFSundayRanks(t *testing.T) {
+	cases := []struct {
+		date string
+		want Rank
+	}{
+		{"2025-11-30", RankClass1}, // Advent I
+		{"2025-12-07", RankClass1}, // Advent II
+		{"2025-12-14", RankClass1}, // Advent III (Gaudete)
+		{"2025-12-21", RankClass1}, // Advent IV
+		{"2025-03-09", RankClass1}, // Lent I
+		{"2025-03-16", RankClass1}, // Lent II
+		{"2025-03-23", RankClass1}, // Lent III
+		{"2025-03-30", RankClass1}, // Lent IV (Laetare)
+		{"2025-04-06", RankClass1}, // Passion Sunday
+		{"2025-04-13", RankClass1}, // Palm Sunday
+		{"2025-04-27", RankClass1}, // Low Sunday
+		{"2025-02-16", RankClass2}, // Septuagesima Sunday -- NOT I class
+		{"2025-02-23", RankClass2}, // Sexagesima Sunday -- NOT I class
+		{"2025-03-02", RankClass2}, // Quinquagesima Sunday -- NOT I class
+		{"2025-06-22", RankClass2}, // II Sunday after Pentecost -- ordinary II class
+	}
+	for _, c := range cases {
+		got := temporalEF(d(c.date))
+		if got.Cel.Rank != c.want {
+			t.Errorf("temporalEF(%s).Cel.Rank = %s, want %s (%s)", c.date, got.Cel.Rank, c.want, got.Cel.Slug)
+		}
+	}
+}
+
+// TestTemporalEFRoseSundays: RG 131 -- rose is permitted on Gaudete (Advent
+// III) and Laetare (Lent IV), for that Sunday's own Office and Mass only.
+// Before the fix, efColour had no Rose case at all.
+func TestTemporalEFRoseSundays(t *testing.T) {
+	if got := temporalEF(d("2025-12-14")).Cel.Colour; got != Rose {
+		t.Errorf("Gaudete (2025-12-14) colour = %s, want rose", got)
+	}
+	if got := temporalEF(d("2025-03-30")).Cel.Colour; got != Rose {
+		t.Errorf("Laetare (2025-03-30) colour = %s, want rose", got)
+	}
+	// The Advent/Lent Sundays either side stay violet -- rose is an indult for
+	// that one Sunday, not a season colour.
+	if got := temporalEF(d("2025-12-07")).Cel.Colour; got != Violet {
+		t.Errorf("Advent II (2025-12-07) colour = %s, want violet", got)
+	}
+	if got := temporalEF(d("2025-03-23")).Cel.Colour; got != Violet {
+		t.Errorf("Lent III (2025-03-23) colour = %s, want violet", got)
+	}
+}
+
+// TestTemporalEFHolyThursdayColour: RG 128(b)/RG 122 -- Holy Thursday's Mass
+// of Chrism and Mass in Cena Domini are white, a whole-day exception to
+// Passiontide's violet. Good Friday and Holy Saturday, either side, stay
+// violet (their own black/no-colour exceptions are a separate, unmodelled
+// gap -- see RG 132, precedence_ef.go's own doc comments).
+func TestTemporalEFHolyThursdayColour(t *testing.T) {
+	easter := d("2025-04-20")
+	holyThu := easter.AddDate(0, 0, -3)
+	goodFri := easter.AddDate(0, 0, -2)
+	holySat := easter.AddDate(0, 0, -1)
+	if got := temporalEF(holyThu).Cel.Colour; got != White {
+		t.Errorf("Holy Thursday colour = %s, want white", got)
+	}
+	if got := temporalEF(goodFri).Cel.Colour; got != Violet {
+		t.Errorf("Good Friday colour = %s, want violet (unchanged)", got)
+	}
+	if got := temporalEF(holySat).Cel.Colour; got != Violet {
+		t.Errorf("Holy Saturday colour = %s, want violet (unchanged)", got)
+	}
+}
+
+// TestTemporalEFEmberDayRanks: RG 91 entry 18 -- the Ember days of Lent (and,
+// unchanged, September and Advent) are II-class privileged ferias, not the
+// ordinary III-class Lenten ferias around them. Before the fix, efEmberSlug
+// had no Lent case at all, so Lent's Ember Wed/Fri/Sat fell through to the
+// ordinary III-class Lenten-feria rank.
+func TestTemporalEFEmberDayRanks(t *testing.T) {
+	// Lent I Sunday 2025 = 2025-03-09; Ember Wed/Fri/Sat = +3/+5/+6.
+	lentI := d("2025-03-09")
+	for _, off := range []int{3, 5, 6} {
+		day := lentI.AddDate(0, 0, off)
+		got := temporalEF(day)
+		if got.Cel.Rank != RankClass2 {
+			t.Errorf("Lent Ember day %s rank = %s, want class-2 (%s)", day.Format("2006-01-02"), got.Cel.Rank, got.Cel.Slug)
+		}
+	}
+}